Petroleum and related products -- Temperature and pressure volume correction factors (petroleum measurement tables) and standard reference conditions

ISO 91:2017 refers to temperature volume correction factors, which allow users to convert volumes, measured at ambient conditions, to those at reference conditions for transactional purposes. This document also refers to compressibility factors required to correct hydrocarbon volumes measured under pressure to the corresponding volumes at the equilibrium pressure for the measured temperature.

Pétrole et produits connexes -- Facteurs de correction de volume par rapport à la température et à la pression (tables de mesure du pétrole) et conditions de référence standard

ISO 91:2017 fait référence aux facteurs de correction de volume par rapport ŕ la température, qui permettent ŕ l'utilisateur de convertir des volumes, mesurés ŕ des conditions ambiantes, en volumes qui auraient été relevés aux conditions de référence ŕ des fins commerciales. Le présent document fait également référence aux facteurs de compressibilité requis pour corriger des volumes d'hydrocarbures mesurés sous une certaine pression afin de les convertir en volumes correspondants ŕ la pression d'équilibre pour la température mesurée.

Naftni in sorodni proizvodi - Volumenski korekcijski faktorji temperature in tlaka (merilne tabele za naftne proizvode) in standardni referenčni pogoji

Ta dokument se nanaša na volumenske korekcijske faktorje temperature, ki uporabnikom omogočajo pretvorbo prostornine,
izmerjene pri običajnih okoljskih pogojih, v prostornino, izmerjeno pri referenčnih pogojih, za namene transakcije. Ta dokument se nanaša tudi na kompresijske faktorje, ki so potrebni za korekcijo prostornine ogljikovodikov, izmerjene pod tlakom, na ustrezno prostornino pri uravnoteženem tlaku za izmerjeno temperaturo.
Preglednica 1 prikazuje opredeljene mejne vrednosti in z njimi povezane enote korekcijskih faktorjev, ki so v tem dokumentu omenjene za surovo nafto, rafinirane proizvode in mazivna olja. Te vrednosti so prikazane v krepki, poševni pisavi.
V tabeli so prikazane tudi mejne vrednosti, pretvorjene v ustrezne enote (in v primeru gostote tudi ostale osnovne temperature). Preglednica 2 prikazuje opredeljene mejne vrednosti korekcijskih faktorjev za lahke ogljikovodike (utekočinjeni zemeljski plin in utekočinjeni naftni plin).

General Information

Status
Published
Publication Date
11-May-2017
Current Stage
6060 - International Standard published
Start Date
04-Mar-2017
Completion Date
12-May-2017

RELATIONS

Effective Date
12-Oct-2013
Effective Date
12-Oct-2013

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INTERNATIONAL ISO
STANDARD 91
First edition
2017-05
Petroleum and related products —
Temperature and pressure volume
correction factors (petroleum
measurement tables) and standard
reference conditions
Pétrole et produits connexes — Facteurs de correction de volume
par rapport à la température et à la pression (tables de mesure du
pétrole) et conditions de référence standard
Reference number
ISO 91:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO 91:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 91:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Sources and usage guidelines for volume correction factors ................................................................................ 2

4.1 Source of volume correction factors ..................................................................................................................................... 2

4.2 Usage guidelines .................................................................................................................................................................................... 3

Annex A (informative) Changes to previous standards ..................................................................................................................... 5

Annex B (normative) Standard reference conditions ......................................................................................................................... 7

Annex C (informative) Titles of petroleum measurement tables given in the API-ASTM-IP-

GPA standards for volume correction factors......................................................................................................................... 8

Annex D (informative) Other volume corrections factors standards ..............................................................................14

Bibliography .............................................................................................................................................................................................................................15

© ISO 2017 – All rights reserved iii
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ISO 91:2017(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical committee ISO/TC 28, Petroleum products and lubricants,

Subcommittee SC 2, Measurement of petroleum and related products.

This first edition cancels and replaces ISO 91-1:1992, ISO 91-2:1991, ISO 9770:1989, and ISO 5024:1999,

which have been technically revised.
iv © ISO 2017 – All rights reserved
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ISO 91:2017(E)
Introduction

Custody transfer of crude petroleum and its products are generally transacted in volumetric quantities.

Since crude oils and petroleum products have relatively high coefficients of thermal expansion and

compressibility, volumes are corrected to standard conditions of temperature and pressure in order

to provide a meaningful and consistent basis for measurement. The definition of standard reference

conditions is therefore of fundamental importance in measurement, calculation and accounting of

petroleum quantities.

Volume correction factors are used to account for the thermal expansion of liquid hydrocarbons

and convert observed volumes to volumes at standard temperature and pressure. Tables of volume

correction factors were originally developed by collecting empirical data relating to the volumetric

change of hydrocarbons over a range of temperatures and pressures. Cooperative international work

on volume correction factors dates from 1932. The temperature volume correction factor tables

[1]

(petroleum measurement tables) referenced in ISO Recommendation (R) 91:1959 were developed

during the late 1940s and published jointly by the American Society of Testing Materials (ASTM) in

[9]

1952 and the Institute of Petroleum (IP) (metric edition) in 1953 . These tables corrected to standard

temperatures of 15 °C and 60 °F only, and were based on data for crude petroleum and petroleum

fractions published in 1916 by the (United States) National Bureau of Standards (NBS) and some later

data on natural gasoline reported in 1942. These 1952 tables were referenced in API/Standard 2540-

[10]

1966 (also designated ASTM D1250-56). A few amendments to ISO/R 91 resulted in the publication

[2] [3]

of a second edition in 1970 . ISO/R 91:1970/Amd 1:1975 was published in 1975 for tables based on a

reference temperature of 20 °C.

In the early 1970s, it was demonstrated that the previously published tables were not satisfactorily

applicable to many crude oils of current economic importance. A revised standard was published

in 1980 by the American Petroleum Institute as the API Manual of Petroleum Measurement

Standards (MPMS) Chapter 11.1 (also designated API/Standard 2540, ASTM D1250-80 and IP 200/80)

following the development of a new database by API in cooperation with the US NBS. This study

included the examination of 463 samples of crude oil and refined products. The crude oil samples

represented 67 % of world production in 1974. The 1980 standard also constituted a major conceptual

departure from previous versions in the recognition of the use of computers in the petroleum industry.

The actual standard represented by API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was

neither the hardcopy printed tables nor the set of equations used to represent the density data, but

was an explicit implementation procedure used to develop computer subroutines. The standardization

of an implementation procedure implied the standardization of the set of mathematical expressions,

including calculational sequence and round-off procedures, used within the computer code. Adherence

to the procedures given in API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was an attempt to

ensure that all computers and computer codes meeting the stated specifications and restrictions would

be able to produce identical results. Hence, the published implementation procedures were the primary

standard, the distributed subroutines the secondary standard, and the published tables produced for

convenience.
[4]

API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was referenced in ISO 91-1:1982 .

[5]
Corrections to the 1980 standard were listed in ISO 91-1:1992 .

Computer implementation procedures developed by the IP for corrections to 20 °C were published

in 1988. These implementation procedures were prepared as standard procedures to enable users

to produce their own computer programmes either for the generation of 20 °C tables or for use in

[8]

calculations without the generation of tables. IP Petroleum Measurement Paper No. 3 was referenced

[6]
in ISO 91-2:1991 , superseding Addendum 1:1975 to ISO/R 91.

Compressibility factors for hydrocarbons in the 0° to 100° API gravity range were developed in 1945

[12]

and published in 1960 as API/Standard 1101 , Appendix B, Table II. This table was superseded by

[13] [14]

API MPMS Chapters 11.2.1 and 11.2.1M published in 1984. API MPMS Chapter 11.2.1M-1984 was

[13]
adopted by ISO/TC 28 and published as ISO 9770:1989 .

Compressibility factors for hydrocarbons in the 0,500 to 0,611 relative density range and 20 °F to 128 °F

[15]

were published in 1984 as API MPMS Chapter 11.2.2 . A second edition of API MPMS Chapter 11.2.2

© ISO 2017 – All rights reserved v
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ISO 91:2017(E)

was published in 1986 with an expanded relative density range of 0,350 to 0,637. A metric version of this

3 3

standard (350 kg/m to 637 kg/m range) was also published in 1986 as API MPMS Chapter 11.2.2M.

Unlike the 1980 temperature correction factor tables (API MPMS Chapter 11.1-1980), the compressibility

table values given in API MPMS Chapters 11.2.1 and 11.2.2 were the standard, not the implementation

procedure for the underlying equations.

In 2004, a revision to API MPMS Chapter 11.1 (also designated as an adjunct to ASTM D1250-04 and

IP 200/04) was published and established procedures for generalized crude oils, liquid refined products,

lubricating oils and individual and special applications, by which volume measurements taken at any

temperature and pressure (within the range of the standard) can be corrected to an equivalent volume

at 15 °C, 60 °F or 20 °C (or other reference temperature) and standard pressure, by use of a correction

factor for temperature and pressure of the liquid (CTPL). API MPMS Chapter 11.1-2004/Adjunct to

ASTM D1250-04/Adjunct to IP 200/04 superseded API MPMS Chapters 11.1-1980, 11.2.1-1984 and

11.2.1M-1984.

In 2007, Addendum 1 to API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04

was published in order to include some minor updates to the standard.

Previously, most natural gas liquid (NGL) and liquefied petroleum gas (LPG) temperature correction

factors were obtained from a variety of sources.
[9] [4]

— ASTM-IP Petroleum Measurement Tables, 1952 , as referenced in ISO/R 91:1970 . This publication

is limited to a 60 °F relative density range of 0,500 and higher.
[16]
— GPA Standard 2142, published in 1957 .
[17]

— GPA Technical Publication TP-16, published in 1988 . It is limited to the following products: HD 5

propane with relative densities of 0,501, 0,505, and 0,510; iso-butane at a relative density of 0,565;

normal butane at a relative density of 0,585, and natural gasoline (12 psia to 14 psia Reid vapour

pressure) at a relative density of 0,664.

— API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 Volume XII, Table 33 “Specific

Gravity Reduction to 60 °F For Liquefied Petroleum Gases and Natural Gasoline”, as referenced in

[5]
ISO 91-1:1992 .

— API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 Volume XII, Table 34 “Reduction of Volume

to 60 °F Against Specific Gravity 60/60 °F For Liquefied Petroleum Gases and Natural Gasoline”, as

[5]
referenced in ISO 91-1:1992 .
[18]
— API/ASTM/GPA Technical Publication TP-25, published in 1988 .

In 2007, these documents were superseded by API MPMS Chapter 11.2.4/GPA Technical Publication TP-27.

vi © ISO 2017 – All rights reserved
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INTERNATIONAL STANDARD ISO 91:2017(E)
Petroleum and related products — Temperature
and pressure volume correction factors (petroleum
measurement tables) and standard reference conditions
1 Scope

This document refers to temperature volume correction factors, which allow users to convert volumes,

measured at ambient conditions, to those at reference conditions for transactional purposes. This

document also refers to compressibility factors required to correct hydrocarbon volumes measured

under pressure to the corresponding volumes at the equilibrium pressure for the measured

temperature.

Table 1 shows the defining limits and their associated units of correction factors referenced in this

document for crude oil, refined products and lubricating oils. These values are shown in bold italics.

Also shown in the table are the limits converted to their equivalent units (and, in the case of the densities,

other base temperatures). Table 2 shows defining limits of correction factors for light hydrocarbons

(natural gas liquids and liquefied petroleum gases).

Table 1 — Defining limits of correction factors for crude oil, refined products and lubricating oils

Crude oil Refined products Lubricating oils
Density, kg/m @ 60 °F 610,6 to 1 163,5 800,9 to 1 163,5
Relative density @ 60 °F 0,611 2 to 1,164 64 0,801 68 to 1,164 6
API gravity @ 60 °F 100 to –10 45 to –10
Density, kg/m @ 15 °C 611,16 to 1 163,79 611,16 to 1 163,86 801,25 to 1 163,85
Density, kg/m @ 20 °C 606,12 to 1 161,15 606,12 to 1 160,62 798,11 to 1 160,71
Temperature, °C –50,00 to 150
Temperature, °F –58,0 to 302
Pressure, psig 0 to 1 500
Pressure, kPa (gauge) 0 to 1,034 × 10
Pressure, bar (gauge) 0 to 103,4
60 °F thermal expansion
−6 −6
factor (α60), per °F 230,3 × 10 to 930,0 × 10
−6 −6
α60, Per °C 414,0 × 10 to 1 674,0 × 10

Table 2 — Defining limits of correction factors for light hydrocarbons (natural gas liquids and

liquefied petroleum gases)
Density, kg/m @ 60 °F 350,0 to 688,0
Density, kg/m @ 15 °C 351,7 to 687,8
Density, kg/m @ 20 °C 331,7 to 683,6
Temperature °C −46,0 to 93,0
Temperature °F −50,8 to 199,4
Saturation conditions (bubble point or saturation vapour
Pressure
pressure) (see Note 2 to 4.1)

This document also specifies standard reference conditions of pressure and temperature for

measurements carried out on crude petroleum and its products, including liquefied petroleum gases

(see Annex B).
© ISO 2017 – All rights reserved 1
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ISO 91:2017(E)

This document excludes specifying standard reference conditions for natural gas which are given in

[15].
ISO 13443
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1–2004 /Adjunct to ASTM

D1250-04 /Adjunct to IP 200/04, Temperature and Pressure Volume Correction Factors for Generalized

Crude Oils, Refined Products, and Lubricating Oils/Addendum 1-2007

API MPMS Chapter 11.2.2-1986, Compressibility Factors for Hydrocarbons: 0.350–0.637 Relative Density

(60 °F/60 °F) and –50 °F to 140 °F Metering Temperature/Errata June 1996

API MPMS Chapter 11.2.2M-1986, Compressibility Factors for Hydrocarbons: 350–637 Kilograms per Cubic

Metre Density (15 °C) and –46 °C to 60 °C Metering Temperature

API MPMS Chapter 11.2.4-2007/GPA Technical Publication TP-27-2007, Temperature Correction for the

Volume of NGL and LPG, Tables 23E, 24E, 53E, 54E, 59E, and 60E

API MPMS Chapter 11.5 Part 1-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 1: Conversions of API gravity at 60° F

API MPMS Chapter 11.5 Part 2-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 2: Conversions for Relative Density (60/60° F)

API MPMS Chapter 11.5 Part 3-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 3: Conversions for Absolute Density at 15° C
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Sources and usage guidelines for volume correction factors
4.1 Source of volume correction factors

For the purpose of custody transfer in accordance with this document, reference shall be made to API

MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04, including Addendum 1-2007.

API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04, including Addendum 1-2007,

recognizes three distinct commodity groups: crude oil, refined products, and lubricating oils. A special

1) Available from API. Order Product Number H11013.
2) Available from ASTM International. Order Product Number ADJD1250-E-PDF.

3) API MPMS Chapter 11.5 Parts 1-3 replaced Volumes XI and XII of API MPMS Chapter 11.1-1980/ASTM

D1250-80/IP 200/80 (see Annex C).
2 © ISO 2017 – All rights reserved
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ISO 91:2017(E)

application category is also included which provides volume correction based on the input of an

experimentally derived coefficient of thermal expansion.

NOTE 1 Additional API volume correction factor standards have subsequently been published or are under

development for particular applications. See Annex D.

API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04 provides general procedures

for the conversion of input data to generate the corrected values at the user specified base temperature

and pressure using the effect of temperature on the liquid (CTL), the compressibility coefficient (F ), the

correction for the effect of pressure on the liquid (CPL), or the correction for temperature and pressure

of a liquid (CTPL), in a form that is consistent with the computation procedures used to generate

VCF values. Two sets of procedures are given for computing the volume correction factor: one set for

data expressed in U.S. customary units (temperature in degrees Fahrenheit, pressure in pounds per

square inch gauge), the other for the metric system of units (temperature in degrees Celsius, pressure

in kilopascals). In contrast to API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80, the metric

procedures require the procedure for U.S. customary units be used first to compute density at 60 °F.

This value is then further corrected to give the metric output.

For density/weight/volume intraconversion, reference shall be made to API MPMS Chapter 11.5

Part 1 to Part 3/Adjunct to ASTM D1250-08 and IP 200/08. These standards provide conversion of

measurements from one system of units to another for both in vacuo and in air values.

For NGL and LPG, reference shall be made to API MPMS Chapter 11.2.4-2007/GPA Technical Publication

TP-27-2007. The implementation procedures describe how to calculate the CTL given an appropriate

density factor at basis temperature and an observed temperature, and calculate the appropriate density

factor at basis temperature given a relative density at an observed temperature. The implementation

procedures are presented in pairs by base temperature. First, the procedures for Tables 23E and 24E of

API MPMS Chapter 11.2.4-2007/GPA TP-27-2007 at a 60 °F base temperature are given. The procedure

for Table 23E makes use of the procedure described in Table 24E, thus Table 24E is presented first.

These are followed by procedures for Table 54E and Table 53E at a base temperature of 15 °C, which

themselves make use of the procedures in Table 23E and Table 24E; these in turn are followed by the

procedures for Table 60E and Table 59E at a base temperature of 20 °C, which also make use of the

procedures described in Table 23E and Table 24E.

To correct NGL and LPG volumes metered under pressure to the corresponding volumes under

equilibrium pressure for the process temperature at the meter, reference shall be made to API MPMS

Chapter 11.2.2-1986 (including Errata June 1996) or API MPMS Chapter 11.2.2M-1986 or if outside of the

density range of these standards, API MPMS Chapter 11.2.1-1984 or API MPMS Chapter 11.2.1M-1984.

These methods require a knowledge of the equilibrium bubble point pressure (vapour pressure)

at the measured conditions. However, the vapour pressure of the process liquid is generally not

measured. The vapour pressure can also be calculated from compositional information, but the

composition is not always measured for natural gas liquids (NGLs). Therefore, a correlation for the

vapour pressure of NGLs based upon normally measured properties is required, and API MPMS

[19]

Chapter 11.2.5-2007/GPA Technical Publication TP-15 can be used for this purpose. The procedure

given in API MPMS Chapter 11.2.5/GPA TP-15 provides a simplified means of estimating equilibrium

vapour pressures of various NGLs from a knowledge of the fluid’s relative density (60 °F/60 °F)

and process temperature. The intended application of this procedure is to provide the values of P

(equilibrium vapour pressure) required to determine the pressure effect contributions to volume

correction factors as specified.

See Annex C for titles of petroleum measurement tables given in the 1980 editions of the API, ASTM,

and IP volume correction factor standards, as well as a list of the documents that have superseded

these documents.
4.2 Usage guidelines

Due to the nature of the changes in this document, it is recognized that guidance concerning an

implementation period might be needed in order to avoid disruptions within the industry and ensure

proper application. As a result, it is recommended that this document be utilized on all new applications

© ISO 2017 – All rights reserved 3
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ISO 91:2017(E)

no later than two years after the publication date. An application for this purpose is defined as the point

where the calculation is applied.

Once the revised standard is implemented in a particular application, the previous standard will no

longer be used in that application.

It is important to note that calculation results for crude oil, refined products or lubricating oils (but

not NGL or LPG) based on ISO 91-1 and ISO 91-2 do not differ significantly from this document. This

document also reflects changes that have been made to the calculation procedures leading to increased

precision. The ranges of the volume correction factor tables referenced in this document have also been

expanded (see Annex A).

If an existing application for crude oil, refined products or lubricating oils (but not NGL or LPG)

complies with ISO 91-1 or ISO 91-2, then it shall be considered in compliance with this document. Once

this document is implemented in a particular application, neither ISO 91-1 nor ISO 91-2 shall be used in

that application.

However, the use of International Standards is voluntary and the decision on when to utilize a standard

is an issue that is subject to the negotiations between the parties involved in the transaction.

NOTE Some ISO density standards might not have comparable discrimination levels to those specified in

this document.
4 © ISO 2017 – All rights reserved
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ISO 91:2017(E)
Annex A
(informative)
Changes to previous standards

Between the initial issuance of the 1980 volume correction factors (for crude oils, refined oils and

lubricating oils as given in API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80) and the mid-

1990s, a number of needs arose within the petroleum industry and a number of enhancements occurred

in computer technology. These needs and enhancements prompted several changes to be made and

incorporated into API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04.

— Previous editions of the printed petroleum measurement tables assumed that density measurements

were made with a glass hydrometer. The odd-numbered printed 1980 petroleum measurement

tables (see Table C.1) all included a hydrometer correction on the observed density. In API MPMS

Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04, no glass hydrometer corrections are

applied. It is assumed that any densities measured with a glass hydrometer will be corrected before

applying the calculations.

— The API MPMS Chapter 11.1-1980 was based on data obtained using the International Practical

Temperature Scale 1968 (IPTS-68). This has been superseded by the International Temperature

Scale 1990 (ITS-90). API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04 takes

this into account by correcting the input temperature values to an IPTS-68 basis before any other

calculations are performed. Standard densities are also adjusted to take into account the small

shifts in the associated standard temperatures.

— The accepted value of the standard density of water at 60 °F has changed slightly from the value

used in the API MPMS Chapter 11.1-1980. This new water density only affects the inter-conversion

of density values with relative density and API gravity. The impact would be seen in Tables 5, 6, 23,

and 24 (see Table C.1) of API MPMS Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200.

— In 1988, the IP produced implementation procedures for 20 °C (Table 59 A, B and D, and Table 60

A, B and D, of API MPMS Chapter 11.1/ASTM D1250/IP 200; see Table C.1) by extending the

procedures used for the 15 °C Tables. This was in response to the needs of countries that use 20 °C

as their standard temperature. Although API never published these tables, they were adopted

[6]

internationally as the reference document for ISO 91-2 . ISO 91-2 complemented ISO 91-1, the

International Standard for temperatures of 60 °F and 15 °C that was based on Volume X of API

MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 (see Table C.1). The 2004 edition of API MPMS

Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200 incorporates the 20 °C volume correction

factors.

— Tables for lubricating oils were developed and approved as a part of the API MPMS Chapter 11.1-1980

but were never fully documented. Only the FORTRAN code was published by the API in Appendix A

and B of the printed 5D and 6D Tables of API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 (see

Table C.1). Implementation procedures for the lubricating oil tables first appeared in Reference [20]

and later in their 20 °C tables. The implementation procedures are now incorporated in API MPMS

Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04.

— For business reasons, the volume correction factors have been extended to lower temperatures and

higher densities, i.e. lower API gravities.

— Real-time density measurement using density meters has become more prevalent in the industry

for input into VCF calculations. These density measurements are often made at pressures greater

than atmospheric. This pressure effect has to be taken into account simultaneously with any

temperature effect when determining the density at standard conditions. Hence, pressure and

temperature corrections have been combined into one procedure.
© ISO 2017 – All rights reserved 5
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ISO 91:2017(E)

— Rounding and truncation of initial and intermediate values have been eliminated. Rounding only

applies to the final VCF values.

— API MPMS Chapter 11.1-1980 used a format that resulted in values for the correction for the effect

of temperature on liquid (CTL) rounded four or five decimal digits, depending upon whether the

CTL value was greater than or less than one. T
...

SLOVENSKI STANDARD
SIST ISO 91:2018
01-junij-2018
1DGRPHãþD
SIST ISO 5024:2001
SIST ISO 91-1:2001
SIST ISO 91-2:2001

1DIWQLLQVRURGQLSURL]YRGL9ROXPHQVNLNRUHNFLMVNLIDNWRUMLWHPSHUDWXUHLQWODND

PHULOQHWDEHOH]DQDIWQHSURL]YRGH LQVWDQGDUGQLUHIHUHQþQLSRJRML

Petroleum and related products - Temperature and pressure volume correction factors

(petroleum measurement tables) and standard reference conditions
Pétrole et produits connexes - Facteurs de correction de volume par rapport à la

température et à la pression (tables de mesure du pétrole) et conditions de référence

standard
Ta slovenski standard je istoveten z: ISO 91:2017
ICS:
75.180.30 Oprema za merjenje Volumetric equipment and
prostornine in merjenje measurements
SIST ISO 91:2018 en,fr

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 91:2018
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SIST ISO 91:2018
INTERNATIONAL ISO
STANDARD 91
First edition
2017-05
Petroleum and related products —
Temperature and pressure volume
correction factors (petroleum
measurement tables) and standard
reference conditions
Pétrole et produits connexes — Facteurs de correction de volume
par rapport à la température et à la pression (tables de mesure du
pétrole) et conditions de référence standard
Reference number
ISO 91:2017(E)
ISO 2017
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SIST ISO 91:2018
ISO 91:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST ISO 91:2018
ISO 91:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Sources and usage guidelines for volume correction factors ................................................................................ 2

4.1 Source of volume correction factors ..................................................................................................................................... 2

4.2 Usage guidelines .................................................................................................................................................................................... 3

Annex A (informative) Changes to previous standards ..................................................................................................................... 5

Annex B (normative) Standard reference conditions ......................................................................................................................... 7

Annex C (informative) Titles of petroleum measurement tables given in the API-ASTM-IP-

GPA standards for volume correction factors......................................................................................................................... 8

Annex D (informative) Other volume corrections factors standards ..............................................................................14

Bibliography .............................................................................................................................................................................................................................15

© ISO 2017 – All rights reserved iii
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SIST ISO 91:2018
ISO 91:2017(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical committee ISO/TC 28, Petroleum products and lubricants,

Subcommittee SC 2, Measurement of petroleum and related products.

This first edition cancels and replaces ISO 91-1:1992, ISO 91-2:1991, ISO 9770:1989, and ISO 5024:1999,

which have been technically revised.
iv © ISO 2017 – All rights reserved
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SIST ISO 91:2018
ISO 91:2017(E)
Introduction

Custody transfer of crude petroleum and its products are generally transacted in volumetric quantities.

Since crude oils and petroleum products have relatively high coefficients of thermal expansion and

compressibility, volumes are corrected to standard conditions of temperature and pressure in order

to provide a meaningful and consistent basis for measurement. The definition of standard reference

conditions is therefore of fundamental importance in measurement, calculation and accounting of

petroleum quantities.

Volume correction factors are used to account for the thermal expansion of liquid hydrocarbons

and convert observed volumes to volumes at standard temperature and pressure. Tables of volume

correction factors were originally developed by collecting empirical data relating to the volumetric

change of hydrocarbons over a range of temperatures and pressures. Cooperative international work

on volume correction factors dates from 1932. The temperature volume correction factor tables

[1]

(petroleum measurement tables) referenced in ISO Recommendation (R) 91:1959 were developed

during the late 1940s and published jointly by the American Society of Testing Materials (ASTM) in

[9]

1952 and the Institute of Petroleum (IP) (metric edition) in 1953 . These tables corrected to standard

temperatures of 15 °C and 60 °F only, and were based on data for crude petroleum and petroleum

fractions published in 1916 by the (United States) National Bureau of Standards (NBS) and some later

data on natural gasoline reported in 1942. These 1952 tables were referenced in API/Standard 2540-

[10]

1966 (also designated ASTM D1250-56). A few amendments to ISO/R 91 resulted in the publication

[2] [3]

of a second edition in 1970 . ISO/R 91:1970/Amd 1:1975 was published in 1975 for tables based on a

reference temperature of 20 °C.

In the early 1970s, it was demonstrated that the previously published tables were not satisfactorily

applicable to many crude oils of current economic importance. A revised standard was published

in 1980 by the American Petroleum Institute as the API Manual of Petroleum Measurement

Standards (MPMS) Chapter 11.1 (also designated API/Standard 2540, ASTM D1250-80 and IP 200/80)

following the development of a new database by API in cooperation with the US NBS. This study

included the examination of 463 samples of crude oil and refined products. The crude oil samples

represented 67 % of world production in 1974. The 1980 standard also constituted a major conceptual

departure from previous versions in the recognition of the use of computers in the petroleum industry.

The actual standard represented by API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was

neither the hardcopy printed tables nor the set of equations used to represent the density data, but

was an explicit implementation procedure used to develop computer subroutines. The standardization

of an implementation procedure implied the standardization of the set of mathematical expressions,

including calculational sequence and round-off procedures, used within the computer code. Adherence

to the procedures given in API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was an attempt to

ensure that all computers and computer codes meeting the stated specifications and restrictions would

be able to produce identical results. Hence, the published implementation procedures were the primary

standard, the distributed subroutines the secondary standard, and the published tables produced for

convenience.
[4]

API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was referenced in ISO 91-1:1982 .

[5]
Corrections to the 1980 standard were listed in ISO 91-1:1992 .

Computer implementation procedures developed by the IP for corrections to 20 °C were published

in 1988. These implementation procedures were prepared as standard procedures to enable users

to produce their own computer programmes either for the generation of 20 °C tables or for use in

[8]

calculations without the generation of tables. IP Petroleum Measurement Paper No. 3 was referenced

[6]
in ISO 91-2:1991 , superseding Addendum 1:1975 to ISO/R 91.

Compressibility factors for hydrocarbons in the 0° to 100° API gravity range were developed in 1945

[12]

and published in 1960 as API/Standard 1101 , Appendix B, Table II. This table was superseded by

[13] [14]

API MPMS Chapters 11.2.1 and 11.2.1M published in 1984. API MPMS Chapter 11.2.1M-1984 was

[13]
adopted by ISO/TC 28 and published as ISO 9770:1989 .

Compressibility factors for hydrocarbons in the 0,500 to 0,611 relative density range and 20 °F to 128 °F

[15]

were published in 1984 as API MPMS Chapter 11.2.2 . A second edition of API MPMS Chapter 11.2.2

© ISO 2017 – All rights reserved v
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SIST ISO 91:2018
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was published in 1986 with an expanded relative density range of 0,350 to 0,637. A metric version of this

3 3

standard (350 kg/m to 637 kg/m range) was also published in 1986 as API MPMS Chapter 11.2.2M.

Unlike the 1980 temperature correction factor tables (API MPMS Chapter 11.1-1980), the compressibility

table values given in API MPMS Chapters 11.2.1 and 11.2.2 were the standard, not the implementation

procedure for the underlying equations.

In 2004, a revision to API MPMS Chapter 11.1 (also designated as an adjunct to ASTM D1250-04 and

IP 200/04) was published and established procedures for generalized crude oils, liquid refined products,

lubricating oils and individual and special applications, by which volume measurements taken at any

temperature and pressure (within the range of the standard) can be corrected to an equivalent volume

at 15 °C, 60 °F or 20 °C (or other reference temperature) and standard pressure, by use of a correction

factor for temperature and pressure of the liquid (CTPL). API MPMS Chapter 11.1-2004/Adjunct to

ASTM D1250-04/Adjunct to IP 200/04 superseded API MPMS Chapters 11.1-1980, 11.2.1-1984 and

11.2.1M-1984.

In 2007, Addendum 1 to API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04

was published in order to include some minor updates to the standard.

Previously, most natural gas liquid (NGL) and liquefied petroleum gas (LPG) temperature correction

factors were obtained from a variety of sources.
[9] [4]

— ASTM-IP Petroleum Measurement Tables, 1952 , as referenced in ISO/R 91:1970 . This publication

is limited to a 60 °F relative density range of 0,500 and higher.
[16]
— GPA Standard 2142, published in 1957 .
[17]

— GPA Technical Publication TP-16, published in 1988 . It is limited to the following products: HD 5

propane with relative densities of 0,501, 0,505, and 0,510; iso-butane at a relative density of 0,565;

normal butane at a relative density of 0,585, and natural gasoline (12 psia to 14 psia Reid vapour

pressure) at a relative density of 0,664.

— API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 Volume XII, Table 33 “Specific

Gravity Reduction to 60 °F For Liquefied Petroleum Gases and Natural Gasoline”, as referenced in

[5]
ISO 91-1:1992 .

— API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 Volume XII, Table 34 “Reduction of Volume

to 60 °F Against Specific Gravity 60/60 °F For Liquefied Petroleum Gases and Natural Gasoline”, as

[5]
referenced in ISO 91-1:1992 .
[18]
— API/ASTM/GPA Technical Publication TP-25, published in 1988 .

In 2007, these documents were superseded by API MPMS Chapter 11.2.4/GPA Technical Publication TP-27.

vi © ISO 2017 – All rights reserved
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SIST ISO 91:2018
INTERNATIONAL STANDARD ISO 91:2017(E)
Petroleum and related products — Temperature
and pressure volume correction factors (petroleum
measurement tables) and standard reference conditions
1 Scope

This document refers to temperature volume correction factors, which allow users to convert volumes,

measured at ambient conditions, to those at reference conditions for transactional purposes. This

document also refers to compressibility factors required to correct hydrocarbon volumes measured

under pressure to the corresponding volumes at the equilibrium pressure for the measured

temperature.

Table 1 shows the defining limits and their associated units of correction factors referenced in this

document for crude oil, refined products and lubricating oils. These values are shown in bold italics.

Also shown in the table are the limits converted to their equivalent units (and, in the case of the densities,

other base temperatures). Table 2 shows defining limits of correction factors for light hydrocarbons

(natural gas liquids and liquefied petroleum gases).

Table 1 — Defining limits of correction factors for crude oil, refined products and lubricating oils

Crude oil Refined products Lubricating oils
Density, kg/m @ 60 °F 610,6 to 1 163,5 800,9 to 1 163,5
Relative density @ 60 °F 0,611 2 to 1,164 64 0,801 68 to 1,164 6
API gravity @ 60 °F 100 to –10 45 to –10
Density, kg/m @ 15 °C 611,16 to 1 163,79 611,16 to 1 163,86 801,25 to 1 163,85
Density, kg/m @ 20 °C 606,12 to 1 161,15 606,12 to 1 160,62 798,11 to 1 160,71
Temperature, °C –50,00 to 150
Temperature, °F –58,0 to 302
Pressure, psig 0 to 1 500
Pressure, kPa (gauge) 0 to 1,034 × 10
Pressure, bar (gauge) 0 to 103,4
60 °F thermal expansion
−6 −6
factor (α60), per °F 230,3 × 10 to 930,0 × 10
−6 −6
α60, Per °C 414,0 × 10 to 1 674,0 × 10

Table 2 — Defining limits of correction factors for light hydrocarbons (natural gas liquids and

liquefied petroleum gases)
Density, kg/m @ 60 °F 350,0 to 688,0
Density, kg/m @ 15 °C 351,7 to 687,8
Density, kg/m @ 20 °C 331,7 to 683,6
Temperature °C −46,0 to 93,0
Temperature °F −50,8 to 199,4
Saturation conditions (bubble point or saturation vapour
Pressure
pressure) (see Note 2 to 4.1)

This document also specifies standard reference conditions of pressure and temperature for

measurements carried out on crude petroleum and its products, including liquefied petroleum gases

(see Annex B).
© ISO 2017 – All rights reserved 1
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SIST ISO 91:2018
ISO 91:2017(E)

This document excludes specifying standard reference conditions for natural gas which are given in

[15].
ISO 13443
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1–2004 /Adjunct to ASTM

D1250-04 /Adjunct to IP 200/04, Temperature and Pressure Volume Correction Factors for Generalized

Crude Oils, Refined Products, and Lubricating Oils/Addendum 1-2007

API MPMS Chapter 11.2.2-1986, Compressibility Factors for Hydrocarbons: 0.350–0.637 Relative Density

(60 °F/60 °F) and –50 °F to 140 °F Metering Temperature/Errata June 1996

API MPMS Chapter 11.2.2M-1986, Compressibility Factors for Hydrocarbons: 350–637 Kilograms per Cubic

Metre Density (15 °C) and –46 °C to 60 °C Metering Temperature

API MPMS Chapter 11.2.4-2007/GPA Technical Publication TP-27-2007, Temperature Correction for the

Volume of NGL and LPG, Tables 23E, 24E, 53E, 54E, 59E, and 60E

API MPMS Chapter 11.5 Part 1-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 1: Conversions of API gravity at 60° F

API MPMS Chapter 11.5 Part 2-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 2: Conversions for Relative Density (60/60° F)

API MPMS Chapter 11.5 Part 3-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 3: Conversions for Absolute Density at 15° C
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Sources and usage guidelines for volume correction factors
4.1 Source of volume correction factors

For the purpose of custody transfer in accordance with this document, reference shall be made to API

MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04, including Addendum 1-2007.

API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04, including Addendum 1-2007,

recognizes three distinct commodity groups: crude oil, refined products, and lubricating oils. A special

1) Available from API. Order Product Number H11013.
2) Available from ASTM International. Order Product Number ADJD1250-E-PDF.

3) API MPMS Chapter 11.5 Parts 1-3 replaced Volumes XI and XII of API MPMS Chapter 11.1-1980/ASTM

D1250-80/IP 200/80 (see Annex C).
2 © ISO 2017 – All rights reserved
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application category is also included which provides volume correction based on the input of an

experimentally derived coefficient of thermal expansion.

NOTE 1 Additional API volume correction factor standards have subsequently been published or are under

development for particular applications. See Annex D.

API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04 provides general procedures

for the conversion of input data to generate the corrected values at the user specified base temperature

and pressure using the effect of temperature on the liquid (CTL), the compressibility coefficient (F ), the

correction for the effect of pressure on the liquid (CPL), or the correction for temperature and pressure

of a liquid (CTPL), in a form that is consistent with the computation procedures used to generate

VCF values. Two sets of procedures are given for computing the volume correction factor: one set for

data expressed in U.S. customary units (temperature in degrees Fahrenheit, pressure in pounds per

square inch gauge), the other for the metric system of units (temperature in degrees Celsius, pressure

in kilopascals). In contrast to API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80, the metric

procedures require the procedure for U.S. customary units be used first to compute density at 60 °F.

This value is then further corrected to give the metric output.

For density/weight/volume intraconversion, reference shall be made to API MPMS Chapter 11.5

Part 1 to Part 3/Adjunct to ASTM D1250-08 and IP 200/08. These standards provide conversion of

measurements from one system of units to another for both in vacuo and in air values.

For NGL and LPG, reference shall be made to API MPMS Chapter 11.2.4-2007/GPA Technical Publication

TP-27-2007. The implementation procedures describe how to calculate the CTL given an appropriate

density factor at basis temperature and an observed temperature, and calculate the appropriate density

factor at basis temperature given a relative density at an observed temperature. The implementation

procedures are presented in pairs by base temperature. First, the procedures for Tables 23E and 24E of

API MPMS Chapter 11.2.4-2007/GPA TP-27-2007 at a 60 °F base temperature are given. The procedure

for Table 23E makes use of the procedure described in Table 24E, thus Table 24E is presented first.

These are followed by procedures for Table 54E and Table 53E at a base temperature of 15 °C, which

themselves make use of the procedures in Table 23E and Table 24E; these in turn are followed by the

procedures for Table 60E and Table 59E at a base temperature of 20 °C, which also make use of the

procedures described in Table 23E and Table 24E.

To correct NGL and LPG volumes metered under pressure to the corresponding volumes under

equilibrium pressure for the process temperature at the meter, reference shall be made to API MPMS

Chapter 11.2.2-1986 (including Errata June 1996) or API MPMS Chapter 11.2.2M-1986 or if outside of the

density range of these standards, API MPMS Chapter 11.2.1-1984 or API MPMS Chapter 11.2.1M-1984.

These methods require a knowledge of the equilibrium bubble point pressure (vapour pressure)

at the measured conditions. However, the vapour pressure of the process liquid is generally not

measured. The vapour pressure can also be calculated from compositional information, but the

composition is not always measured for natural gas liquids (NGLs). Therefore, a correlation for the

vapour pressure of NGLs based upon normally measured properties is required, and API MPMS

[19]

Chapter 11.2.5-2007/GPA Technical Publication TP-15 can be used for this purpose. The procedure

given in API MPMS Chapter 11.2.5/GPA TP-15 provides a simplified means of estimating equilibrium

vapour pressures of various NGLs from a knowledge of the fluid’s relative density (60 °F/60 °F)

and process temperature. The intended application of this procedure is to provide the values of P

(equilibrium vapour pressure) required to determine the pressure effect contributions to volume

correction factors as specified.

See Annex C for titles of petroleum measurement tables given in the 1980 editions of the API, ASTM,

and IP volume correction factor standards, as well as a list of the documents that have superseded

these documents.
4.2 Usage guidelines

Due to the nature of the changes in this document, it is recognized that guidance concerning an

implementation period might be needed in order to avoid disruptions within the industry and ensure

proper application. As a result, it is recommended that this document be utilized on all new applications

© ISO 2017 – All rights reserved 3
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SIST ISO 91:2018
ISO 91:2017(E)

no later than two years after the publication date. An application for this purpose is defined as the point

where the calculation is applied.

Once the revised standard is implemented in a particular application, the previous standard will no

longer be used in that application.

It is important to note that calculation results for crude oil, refined products or lubricating oils (but

not NGL or LPG) based on ISO 91-1 and ISO 91-2 do not differ significantly from this document. This

document also reflects changes that have been made to the calculation procedures leading to increased

precision. The ranges of the volume correction factor tables referenced in this document have also been

expanded (see Annex A).

If an existing application for crude oil, refined products or lubricating oils (but not NGL or LPG)

complies with ISO 91-1 or ISO 91-2, then it shall be considered in compliance with this document. Once

this document is implemented in a particular application, neither ISO 91-1 nor ISO 91-2 shall be used in

that application.

However, the use of International Standards is voluntary and the decision on when to utilize a standard

is an issue that is subject to the negotiations between the parties involved in the transaction.

NOTE Some ISO density standards might not have comparable discrimination levels to those specified in

this document.
4 © ISO 2017 – All rights reserved
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SIST ISO 91:2018
ISO 91:2017(E)
Annex A
(informative)
Changes to previous standards

Between the initial issuance of the 1980 volume correction factors (for crude oils, refined oils and

lubricating oils as given in API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80) and the mid-

1990s, a number of needs arose within the petroleum industry and a number of enhancements occurred

in computer technology. These needs and enhancements prompted several changes to be made and

incorporated into API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04.

— Previous editions of the printed petroleum measurement tables assumed that density measurements

were made with a glass hydrometer. The odd-numbered printed 1980 petroleum measurement

tables (see Table C.1) all included a hydrometer correction on the observed density. In API MPMS

Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04, no glass hydrometer corrections are

applied. It is assumed that any densities measured with a glass hydrometer will be corrected before

applying the calculations.

— The API MPMS Chapter 11.1-1980 was based on data obtained using the International Practical

Temperature Scale 1968 (IPTS-68). This has been superseded by the International Temperature

Scale 1990 (ITS-90). API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04 and IP 200/04 takes

this into account by correcting the input temperature values to an IPTS-68 basis before any other

calculations are performed. Standard densities are also adjusted to take into account the small

shifts in the associated standard temperatures.

— The accepted value of the standard density of water at 60 °F has changed slightly from the value

used in the API MPMS Chapter 11.1-1980. This new water density only affects the inter-conversion

of density values with relative density and API gravity. The impact would be seen in Tables 5, 6, 23,

and 24 (see Table C.1) of API MPMS Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200.

— In 1988, the IP produced implementation procedures for 20 °C (Table 59 A, B and D, and Table 60

A, B and D, of API MPMS Chapter 11.1/ASTM D1250/IP 200; see Table C.1) by extending the

procedures used for the 15 °C Tables. This was in response to the needs of countries that use 20 °C

as their standard temperature. Although API never published these tables, they were adopted

[6]

internationally as the reference document for ISO 91-2 . ISO 91-2 complemented ISO 91-1, the

International Standard for temperatures of 60 °F and 15 °C that was based on Volume X of API

MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 (see Table C.1). The 2004 edition of API MPMS

Chapter 11.1/Adjunct to ASTM D1250/Adjunct to IP 200 incorporates the 20 °C volume correction

factors.

— Tables for lubricating oils were developed and approved as a part of the API MPMS Chapter 11.1-1980

but were never fully documented. Only the FORTRAN code was published by the API in Appendix A

and B of the printed 5D and 6D Tables of API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 (see

Table C.1). Implementation procedures for the lubricating oil tables first appeared in Reference [20]

and la
...

NORME ISO
INTERNATIONALE 91
Première édition
2017-05
Pétrole et produits connexes —
Facteurs de correction de volume
par rapport à la température et à
la pression (tables de mesure du
pétrole) et conditions de référence
standard
Petroleum and related products — Temperature and pressure volume
correction factors (petroleum measurement tables) and standard
reference conditions
Numéro de référence
ISO 91:2017(F)
ISO 2017
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ISO 91:2017(F)
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ISO 91:2017(F)
Sommaire Page

Avant-propos ..............................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 2

3 Termes et définitions ....................................................................................................................................................................................... 2

4 Origines des facteurs de correction de volume et lignes directrices d’utilisation ..........................3

4.1 Origines des facteurs de correction de volume ........................................................................................................... 3

4.2 Lignes directrices d’utilisation .................................................................................................................................................. 4

Annexe A (informative) Modifications apportées aux normes précédentes ...............................................................5

Annexe B (normative) Conditions de référence standard .............................................................................................................. 7

Annexe C (informative) Titres des tables de mesure du pétrole données dans les normes

API-ASTM-IP-GPA pour les facteurs de correction de volume ............................................................................... 8

Annexe D (informative) Autres normes sur les facteurs de correction du volume ...........................................15

Bibliographie ...........................................................................................................................................................................................................................16

© ISO 2017 – Tous droits réservés iii
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ISO 91:2017(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www

.iso .org/ directives).

L’attention est appelée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de

brevets reçues par l’ISO (voir www .iso .org/ brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, la signification des termes et expressions

spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion

de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles

techniques au commerce (OTC), voir le lien suivant: w w w . i s o .org/ iso/ fr/ avant -propos .html

Le présent document a été élaboré par le comité technique ISO/TC 28, Produits pétroliers et produits

connexes d’origine synthétique ou biologique, sous-comité SC 2, Mesurage du pétrole et des produits

connexes.

Cette première édition annule et remplace l’ISO 91-1:1992, l’ISO 91-2:1991, l’ISO 9770:1989 et

l’ISO 5024:1999, qui ont fait l’objet d’une révision technique.
iv © ISO 2017 – Tous droits réservés
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ISO 91:2017(F)
Introduction

Les transactions du commerce international du pétrole brut et de ses sous-produits sont en général

fixées par rapport aux volumes. Étant donné que les pétroles bruts et produits pétroliers présentent

des coefficients de dilatation thermique et de compressibilité relativement élevés, les volumes sont

corrigés par rapport aux conditions standard de température et de pression afin de disposer d’une

base de mesure significative et cohérente. La définition des conditions de référence standard est par

conséquent de la plus haute importance pour le mesurage, le calcul et la facturation des volumes de

produits pétroliers.

Des facteurs de correction de volume sont utilisés pour tenir compte de la dilatation thermique des

hydrocarbures liquides et convertir les volumes observés en volumes aux conditions standard de

température et de pression. Des tables de facteurs de correction de volume ont été initialement

développées par recueil de données empiriques sur les variations volumiques d’hydrocarbures sur

une plage donnée de températures et de pressions. Le travail international coopératif sur les facteurs

de correction de volume date de 1932. Les tables de facteurs de correction de volume basées sur les

[1]

températures (tables de mesure du pétrole) référencées dans la Recommandation ISO (R) 91:1959

ont été élaborées à la fin des années 1940 et ont été publiées conjointement par l’American Society of

[9]

Testing Materials (ASTM) en 1952 et l’Institute of Petroleum (IP) (édition avec unités SI) en 1953 . Ces

tables ont établi les corrections pour une conversion aux températures standard de 15 °C et de 60 °F

uniquement, et sont basées sur des données concernant le pétrole brut et des sous-produits pétroliers

publiées en 1916 par le bureau américain de normalisation, le National Bureau of Standards (NBS), et

sur des données plus récentes sur l’essence de gaz naturel parues en 1942. Ces tables de 1952 sont

[10]

référencées dans la norme API/Standard 2540-1966 (appelée également ASTM D1250-56). Quelques

modifications ont été apportées à l’ISO/R 91, qui, de ce fait, a fait l’objet d’une deuxième édition publiée

[2] [3]

en 1970 . L»ISO/R 91:1970/Am 1:1975 est paru en 1975 pour inclure des tables basées sur une

température de référence de 20 °C.

Au début des années 1970, il a été démontré que les tables précédemment publiées n’étaient pas

applicables de manière satisfaisante à nombre de pétroles bruts qui représentaient déjà des enjeux

économiques importants. Une norme révisée a été publiée en 1980 par l’American Petroleum Institute

sous le titre de API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1 (également

appelée norme API/Standard 2540, ASTM D1250-80 et IP 200/80) suite à l’élaboration d’une nouvelle

base de données par l’API en coopération avec l’US NBS (bureau américain de normalisation).

Cette étude est basée sur l’analyse de 463 échantillons de pétrole brut et de produits raffinés. Ces

échantillons de pétrole brut représentaient 67 % de la production mondiale en 1974. La norme de 1980

a également constitué un point de départ conceptuel majeur par rapport aux versions précédentes

dans la reconnaissance de l’utilisation des ordinateurs dans l’industrie pétrolière. Cette édition de la

norme portant la référence API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 ne correspondait

ni aux tables au format papier, ni à l’ensemble des équations utilisées pour représenter les données de

masse volumique, mais était une procédure explicite de mise en œuvre utilisée pour développer des

sous-programmes informatiques. La normalisation d’une procédure de mise en œuvre impliquait la

normalisation de l’ensemble d’expressions mathématiques, notamment de la séquence de calcul et des

procédures d’arrondissement, utilisées dans le code informatique. L’adoption des procédures données

dans l’API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 visait à garantir que tous les ordinateurs

et codes informatiques respectant les spécifications et restrictions mentionnées aboutiraient aux

mêmes résultats. Par conséquent, les procédures de mise en œuvre publiées ont constitué la norme

principale, les sous-programmes répartis, la norme secondaire et les tables publiées dans un souci de

commodité.
[4]

L’API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 a été référencé dans l’ISO 91-1:1982 . Les

[5]

corrections apportées à la norme de 1980 ont été répertoriées dans l’ISO 91-1:1992 .

Les procédures de mise en œuvre informatique développées par l’IP pour des conversions à 20 °C

ont été publiées en 1988. Ces procédures de mise en œuvre ont été préparées comme des procédures

standard pour permettre aux utilisateurs de construire leurs propres programmes informatiques

destinés soit à générer des tables basées sur une température de 20 °C, soit à être utilisés dans des

© ISO 2017 – Tous droits réservés v
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ISO 91:2017(F)
[8]

calculs sans générer de tables. Le document IP Petroleum Measurement Paper No. 3 a été référencé

[6]
dans l’ISO 91-2:1991 , supplantant l’Addendum 1:1975 à l’ISO/R 91.

Les facteurs de compressibilité des hydrocarbures dans la plage de densité API entre 0° et 100° ont été

[12]

développés en 1945 et publiés en 1960 en tant que norme API/Standard 1101 , Appendix B, Table II.

[13] [14]

Cette table a été remplacée par l’API MPMS Chapters 11.2.1 et 11.2.1M publié en 1984. L’API MPMS

[13]

Chapter 11.2.1M-1984 a été adopté par l’ISO/TC 28 et publié sous la référence ISO 9770:1989 .

Les facteurs de compressibilité des hydrocarbures dans la plage de densité relative entre 0,500 et 0,611,

[15]

et dans la plage de 20 °F à 128 °F ont été publiés en 1984 en tant que API MPMS Chapter 11.2.2 .

Une deuxième édition de l’API MPMS Chapter 11.2.2 est parue en 1986 avec une plage de densité

relative étendue allant de 0,350 à 0,637. Une version de cette norme en unités SI (plage de 350 kg/m

à 637 kg/m ) a également été publiée en 1986 en tant que API MPMS Chapter 11.2.2M.

Contrairement aux tables de facteurs de correction basées sur les températures de 1980 (API MPMS

Chapter 11.1-1980), les valeurs des tables de compressibilité données dans l’API MPMS Chapters 11.2.1

et 11.2.2 constituent la norme, et non la procédure de mise en œuvre pour les équations sous-jacentes.

En 2004, une révision de l’API MPMS Chapter 11.1 (également appelée adjunct to ASTM D1250-04 et

Adjunct to IP 200/04) a été publiée et a établi des procédures pour les pétroles bruts, les produits

raffinés liquides, les huiles lubrifiantes et des applications particulières et spéciales, grâce auxquelles les

mesures de volume relevées à n’importe quelles température et pression (dans les limites de la plage de la

norme) peuvent être corrigées de manière à être converties en volume équivalent à 15 °C, 60 °F ou 20 °C

(ou à une autre température de référence) et à pression standard, à l’aide d’un facteur de correction

pour la température et la pression du liquide (correction CTPL). L’API MPMS Chapter 11.1-2004/Adjunct

to ASTM D1250-04/Adjunct to IP 200/04 a remplacé l’API MPMS Chapters 11.1-1980, 11.2.1-1984

et 11.2.1M-1984.

En 2007, l’Addendum 1 to API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to

IP 200/04 a été publié afin d’inclure plusieurs modifications mineures apportées à la norme.

Précédemment, la plupart des facteurs de correction de température des liquides de gaz naturel (GNL)

et des gaz de pétrole liquéfiés (GPL) ont été obtenus à partir de sources diverses:

[9]

— le document ASTM-IP Petroleum Measurement Tables (Tables de mesure du pétrole), 1952 , comme

[4]

référencé dans l’ISO/R 91:1970 . Cette publication est limitée à la plage des densités relatives à

60 °F supérieures ou égales à 0,500;
[16]
— la norme GPA Standard 2142, publiée en 1957 ;
[17]

— la publication technique GPA Technical Publication TP-16, publiée en 1988 . Cette dernière est

limitée aux produits suivants: propane HD-5 de densité relative égale à 0,501, 0,505, et 0,510; iso-

butane de densité relative égale à 0,565; butane normal de densité relative égale à 0,585, et essence

de gaz naturel (pression de vapeur Reid comprise entre 12 psia et 14 psia) de densité relative égale

à 0,664;

— le document API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 Volume XII, Table 33 «Specific

Gravity Reduction to 60 °F For Liquefied Petroleum Gases and Natural Gasoline» (conversion à 60 °F

de la densité relative pour les gaz de pétrole liquéfiés et les essences de gaz naturel), comme référencé

[5]
dans l’ISO 91-1:1992 ;

— le document API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 Volume XII, Table 34

«Reduction of Volume to 60 °F Against Specific Gravity 60/60 °F For Liquefied Petroleum Gases and

Natural Gasoline» (conversion à 60 °F des volumes en fonction de la densité relative 60/60 °F pour les

[5]

gaz de pétrole liquéfiés et les essences de gaz naturel), comme référencé dans l’ISO 91-1:1992 ;

[18]
— le document API/ASTM/GPA Technical Publication TP-25, publié en 1988 .

En 2007, ces documents ont été remplacés par l’API MPMS Chapter 11.2.4/GPA Technical Publication TP-27.

vi © ISO 2017 – Tous droits réservés
---------------------- Page: 6 ----------------------
NORME INTERNATIONALE ISO 91:2017(F)
Pétrole et produits connexes — Facteurs de correction
de volume par rapport à la température et à la pression
(tables de mesure du pétrole) et conditions de référence
standard
1 Domaine d’application

Le présent document fait référence aux facteurs de correction de volume par rapport à la température,

qui permettent à l’utilisateur de convertir des volumes, mesurés à des conditions ambiantes, en volumes

qui auraient été relevés aux conditions de référence à des fins commerciales. Le présent document fait

également référence aux facteurs de compressibilité requis pour corriger des volumes d’hydrocarbures

mesurés sous une certaine pression afin de les convertir en volumes correspondants à la pression

d’équilibre pour la température mesurée.

Le Tableau 1 présente les limites de définition et leurs unités associées pour les facteurs de correction

référencés dans le présent document pour le pétrole brut, les produits raffinés et les huiles lubrifiantes.

Ces valeurs sont indiquées en italique et en gras. Le tableau présente également les conversions des

limites exprimées selon d’autres unités équivalentes (et, dans le cas des masses volumiques, selon

d’autres températures de base). Le Tableau 2 présente les limites de définition des facteurs de correction

pour les hydrocarbures légers (liquides de gaz naturel et gaz de pétrole liquéfiés).

Tableau 1 — Limites de définition des facteurs de correction pour le pétrole brut, les produits

raffinés et les huiles lubrifiantes
Pétrole brut Produits raffinés Huiles lubrifiantes
Masse volumique, kg/m à 60 °F 610,6 à 1 163,5 800,9 à 1 163,5
Densité relative à 60 °F 0,611 2 à 1,164 64 0,801 68 à 1,164 6
Densité API à 60 °F 100 à –10 45 à –10

Masse volumique, kg/m à 15 °C 611,16 à 1 163,79 611,16 à 1 163,86 801,25 à 1 163,85

Masse volumique, kg/m à 20 °C 606,12 à 1 161,15 606,12 à 1 160,62 798,11 à 1 160,71

Température, °C –50,00 à 150
Température, °F –58,0 à 302
Pression, psig 0 à 1 500
Pression, kPa (manométrique) 0 à 1,034 × 10
Pression, bar (manométrique) 0 à 103,4
Facteur de dilatation thermique
−6 −6
230,3 × 10 à 930,0 × 10
à 60 °F (α60), par °F
−6 −6
α60, par °C 414,0 × 10 à 1 674,0 × 10
© ISO 2017 – Tous droits réservés 1
---------------------- Page: 7 ----------------------
ISO 91:2017(F)

Tableau 2 — Limites de définition des facteurs de correction pour les hydrocarbures légers

(liquides de gaz naturel et gaz de pétrole liquéfiés)
Masse volumique, kg/m à 60 °F 350,0 à 688,0
Masse volumique, kg/m à 15 °C 351,7 à 687,8
Masse volumique, kg/m à 20 °C 331,7 à 683,6
Température °C −46,0 à 93,0
Température °F −50,8 à 199,4
Pression Conditions de saturation (point d’ébullition ou pression de
vapeur de saturation) – voir Note 2 à 4.1

Le présent document spécifie également des conditions de référence standard de température et de

pression pour les mesurages effectués sur le pétrole brut et ses sous-produits, notamment les gaz de

pétrole liquéfiés (voir Annexe B).

Le présent document exclut la spécification des conditions de référence standard pour le gaz naturel,

[15]
lesquelles sont données dans l’ISO 13443 .
2 Références normatives

Les documents suivants, en totalité ou en partie, sont référencés normativement dans ce documents

et sont indispensables pour son application. Pour les références datées, seule l’édition citée s’applique.

Pour les références non datées, la dernière édition du document de référence s’applique (y compris les

éventuels amendements).

API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1–2004 /Adjunct to ASTM

D1250-04 /Adjunct to IP 200/04, Temperature and Pressure Volume Correction Factors for Generalized

Crude Oils, Refined Products, and Lubricating Oils/Addendum 1-2007

API MPMS Chapter 11.2.2-1986, Compressibility Factors for Hydrocarbons: 0.350–0.637 Relative Density

(60 °F/60 °F) and –50 °F to 140 °F Metering Temperature/Errata June 1996

API MPMS Chapter 11.2.2M-1986, Compressibility Factors for Hydrocarbons: 350–637 Kilograms per Cubic

Metre Density (15 °C) and –46 °C to 60 °C Metering Temperature

API MPMS Chapter 11.2.4-2007/GPA Technical Publication TP-27-2007, Temperature Correction for the

Volume of NGL and LPG, Tables 23E, 24E, 53E, 54E, 59E, and 60E

API MPMS Chapter 11.5 Part 1-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 1: Conversions of API gravity at 60 °F

API MPMS Chapter 11.5 Part 2-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 2: Conversions for Relative Density (60/60 °F)

API MPMS Chapter 11.5 Part 3-2009/Adjunct to ASTM D1250-08/Adjunct to IP 200/08, Density/Weight/

Volume Intraconversion — Part 3: Conversions for Absolute Density at 15 °C
3 Termes et définitions
Aucun terme ni aucune définition ne sont donnés dans ce document.
1) Disponible sur CD-ROM chez l’API. Référence produit H11013

2) Disponible sur CD-ROM chez ASTM International Headquarters. Référence produit ADJD1250CD

3) API MPMS Chapter 11.5 Parts 1-3 remplace les Volumes XI et XII de l’API MPMS Chapter 11.1-1980/ASTM

D1250-80/IP 200/80 (voir Annexe B).
2 © ISO 2017 – Tous droits réservés
---------------------- Page: 8 ----------------------
ISO 91:2017(F)

L’ISO et la IEC tiennent à jour des bases de données terminologiques pour la normalisation aux adresses

suivantes:
— Electropedia IEC: consultable sur http:// www .electropedia .org/

— Plateforme ISO de navigation en ligne: consultable sur http:// www .iso .org/ obp

4 Origines des facteurs de correction de volume et lignes directrices d’utilisation

4.1 Origines des facteurs de correction de volume

Pour le commerce international en accord avec le présent document, il doit être fait référence à l’API MPMS

Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04, incluant l’Addendum 1-2007.

L’API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04, incluant

l’Addendum 1-2007, fait la distinction entre les trois groupes de produits suivants: pétrole brut,

produits raffinés, et huiles lubrifiantes. Une catégorie d’application spéciale est également incluse,

laquelle indique une correction de volume basée sur l’entrée d’un coefficient de dilatation thermique

obtenu expérimentalement.

NOTE 1 Des normes complémentaires sur le facteur de correction de volume API ont été publiées

ultérieurement ou sont en cours d’élaboration pour des applications particulières. Voir Annexe D.

L’API MPMS Chapter 11.1-2004/Adjunct to ASTM D1250-04/Adjunct to IP 200/04 délivre des procédures

générales de conversion des données d’entrée pour générer les valeurs corrigées à la température et à

la pression de base spécifiées par l’utilisateur, utilisant la correction de l’effet de la température sur le

liquide (correction CTL), le coefficient de compressibilité (F ), la correction de l’effet de la pression sur

le liquide (correction CPL), ou la correction pour la température et la pression d’un liquide (correction

CTPL), selon une forme qui est cohérente avec les procédures de calcul utilisées pour générer des

valeurs de facteur de correction de volume (facteur VCF). Deux ensembles de procédures sont donnés

pour le calcul du facteur de correction de volume: un ensemble pour les données exprimées en unités

de mesure américaines (température en degrés Fahrenheit, pression manométrique en livres par pouce

carré (psig)), l’autre ensemble pour le système d’unités SI (température en degrés Celsius, pression en

kilopascal). Contrairement à l’API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80, les procédures

avec unités SI nécessite d’utiliser la procédure pour les unités de mesure américaines pour calculer la

masse volumique à 60 °F. Cette valeur est ensuite corrigée pour donner un résultat en unités SI.

Pour l’intraconversion de masse volumique/masse/volume, il doit être fait référence à l’API MPMS

Chapter 11.5 Part 1 à Part 3/Adjunct to ASTM D1250-08/Adjunct to IP 200/08. Ces normes spécifient la

conversion des mesures d’un système d’unités à l’autre pour des valeurs obtenues sous vide et dans l’air.

Pour les GNL et les GPL, il doit être fait référence à l’API MPMS Chapter 11.2.4-2007/GPA Technical

Publication TP-27-2007. Les procédures de mise en œuvre décrivent la manière de calculer la correction

CTL à partir d’un facteur de masse volumique adéquat à une température de base et à une température

observée, et de calculer le facteur de masse volumique adéquat à une température de base à partir

d’une densité relative à une température observée. Les procédures de mise en œuvre sont présentées

par paires pour chaque température de base. Les procédures des Tables 23E et 24E de l’API MPMS

Chapter 11.2.4-2007/GPA TP-27-2007 à une température de base de 60 °F sont données en premier.

La procédure de la Table 23E utilise la procédure décrite dans la Table 24E, c’est pourquoi la Table

24E est présentée en premier. Ces procédures sont suivies des procédures des Tables 54E et 53E à

une température de base de 15 °C, lesquelles utilisent les procédures des Tables 23E et 24E et sont à

leur tour suivies des procédures des Tables 60E et 59E à une température de base de 20 °C, lesquelles

utilisent les procédures décrites dans les Tables 23E et 24E.

Pour corriger les volumes de GNL et de GPL mesurés sous une certaine pression de manière à les

convertir en volumes correspondants sous pression d’équilibre pour la température de la procédure

telle que mesurée, il doit être fait référence à l’API MPMS Chapter 11.2.2-1986 (incluant les Errata de

juin 1996) ou à l’API MPMS Chapter 11.2.2M-1986 ou si la masse volumique se trouve hors de l’intervalle

de ces normes, API MPMS Chapter 11.2.1-1984 ou API MPMS Chapter 11.2.1M-1984.
© ISO 2017 – Tous droits réservés 3
---------------------- Page: 9 ----------------------
ISO 91:2017(F)

Ces méthodes nécessitent de connaître la pression du point d’ébullition à l’équilibre (pression de vapeur)

aux conditions mesurées. Cependant, la pression de vapeur du liquide de procédé n’est en général pas

mesurée. La pression de vapeur peut également être calculée d’après des informations de composition,

mais la composition n’est pas toujours mesurée pour les liquides de gaz naturel (GNL). Par conséquent,

une corrélation pour la pression de vapeur des GNL fondée sur des propriétés qui sont normalement

[19]

mesurées est requise, et l’API MPMS Chapter 11.2.5-2007/GPA Technical Publication TP-15 peut être

utilisé à cette fin. La procédure donnée dans l’API MPMS Chapter 11.2.5/GPA TP-15 donne un moyen

simplifié pour estimer les pressions de vapeur à l’équilibre de divers GNL à partir de valeurs connues

de densité relative (60 °F/60 °F) et de température de procédé du fluide. L’application prévue de cette

procédure est de donner les valeurs de P (pression de vapeur à l’équilibre) requises pour déterminer

les contributions de l’effet de pression sur les facteurs de correction de volume comme spécifié.

Se reporter à l’Annexe C pour connaître les titres des tables de mesure du pétrole données dans les

éditions de 1980 des normes API, ASTM et IP sur le facteur de correction de volume, et la liste des

documents ayant remplacé ces documents.
4.2 Lignes directrices d’utilisation

En raison de la nature des modifications incluses dans le présent document, il est admis que des

préconisations concernant une période de mise en œuvre pourraient être nécessaires pour éviter des

perturbations dans l’industrie et garantir une application correcte. En conséquence, il est recommandé

d’appliquer le présent document à toutes les nouvelles applications de moins de deux ans à compter de

la date de publication. Une application dans ce contexte est définie comme le point au niveau duquel le

calcul est appliqué.

Une fois la norme révisée mise en œuvre dans une application particulière, la norme précédente ne sera

plus utilisée pour cette application.

Il est important de noter que les résultats des calculs pour le pétrole brut, les produits raffinés ou les

huiles lubrifiantes (mais pas pour les GNL ou les GPL) basés sur l’ISO 91-1 et l’ISO 91-2 ne s’écartent pas

de manière significative du présent document. Le présent document reflète également les modifications

qui ont été apportées aux procédures de calcul conduisant à une meilleure précision. Les plages des

tables de facteur de correction de volume référencées dans le présent document ont été étendues (voir

Annexe A).

Si une application existante pour le pétrole brut, les produits raffinés ou les huiles lubrifiantes (mais pas

pour les GNL ou les GPL) est conforme à l’ISO 91-1 ou à l’ISO 91-2, elle doit alors être considérée comme

conforme au présent document. Une fois ce document mis en œuvre dans une application particulière,

ni l’ISO 91-1 ni l’ISO 91-2 ne doivent être utilisées dans cette application.

Néanmoins, l’utilisation de Normes internationales est facultative et la décision sur quand utiliser une

norme est une question qui est soumise à négociations entre les parties impliquées dans la transaction.

NOTE Certaines normes ISO de détermination de la masse volumique pourraient ne pas avoir de niveaux de

discrimination comparables à ceux spécifiés dans le présent document.
4 © ISO 2017 – Tous droits réservés
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ISO 91:2017(F)
Annexe A
(informative)
Modifications apportées aux normes précédentes

Entre la première publication des facteurs de correction de volume de 1980 (pour les

pétroles bruts, les pétroles raffinés et les huiles lubrifiantes tels que donnés dans l’API MPMS

Chapter 11.1-1980/ASTM D1250-80/IP 200/80) et le milieu des années 1990, un certain nombre de

besoins sont apparus dans l’industrie pétrolière et un certain nombre d’améliorations ont été mises

en place dans la technologie informatique. Ces besoins et améliorations ont conduit à apporter et

intégrer plusieurs modifications à l’API MPMS Chapter 1
...

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